Air to air missiles (AAMs) differ principally in guidance,the two broad groups being radar guided and heat-seeking or infra-red(IR) missiles. Of the two categories, the second, by virtue of it'ssimplicity and lower demands on launch aircraft complexity, has becomethe numerically superior, arming high performance fighters like theF-15or F-14 operated by frontline air forces, yet also equipping vintage1950's fighters, defending Third World countries.
The initial deployment of heat seeking missiles began in thelate 1950's, with the USAF acquiring it's first AIM-4 Falcons and AIM-9Sidewinders, however, it was not until the Viet-Nam war that the AIM-9saw widespread use. The weapon was not as successful as expected,reliability was a particular problem, especially with the USN (repeatedcarrier launches and recoveries - quote ''banging them on the deckafterevery flight''), but when the missile did work, it was effective, whichmay be confirmed by a number of NVAF pilots who had the uniqueexperience of a 'Winder entering the tailpipe of their sturdy Mikoyan,resulting in it's subsequent bisection.
As their name implies, heat-seeking missiles home on to thehot areas of a target. The target will usually both reflect and emitinfra-red radiation, which propagates through the atmosphere, losingit's intensity due to number of effects. This radiation is detected bythe missile's seeker head, which, if the conditions are right, willthenprovide the guidance with the relative position of the target enablingthe weapon to home in and destroy the target. In order to fullyappreciate the problems involved in creating an effective weapon ofthiskind, we must examine the behaviour of infra-red radiation, thecharacteristics of an aircraft as a source of IR energy, the manner inwhich this energy travels through the atmosphere and finally, how themissile seeker processes it to gain information as to the target'sposition.
The aircraft as an intrinsic source of IR energy and thereasonably good propagation of IR clearly indicate the potential forrelatively simple, accurate short range missile guidance. As the targetitself emits all the energy needed for detection and guidance theweaponmay be fire-and-forget, without the need for complex and cumbersomefirecontrol and illuminating radar. As a relatively simple system, theweapon may be smaller and lighter, it's fire-and-forget ability makesit then ideal as a dogfight weapon, complementing cannon. This reflectsin the widespread use of such weapons, eg the AIM-9J/L with the F-16,the R.550 Magic/Mirage III/F1 or the Israeli Rafael Shafrir used withvirtually all IAF fighter aircraft, not to speak of the K-13A Atoll orthe AA-8 Aphid used by Warpac air forces.
A guided missile can be broken down into three systems,guidance and control, warhead and propulsion, all fitted to anairframe.Propulsion is usually provided by a solid propellant rocket with a burntime of the order of seconds, this is adequate for acceleration tospeeds cca 3.5M. The warhead is usually small in weapons of this class,as it is assumed the missile will detonate either on the target orwithin it, warheads are commonly high explosive/fragmentation types .Most weapons employ a combination of proximity and impact fusing.
The guidance and control systems of the missile occupy it'snose section, the guidance senses the position of the target and issuescommands to the servoes in the control section which then actuate thecontrol surfaces to achieve the desired flightpath correction. The vastmajority of operational IR guided missiles employ a canard controlsurface/tail stabiliser configuration, the type of canard employedusually betraying the particular emphasis placed during design, eg thestabilising fins fore of the canards on the R.550 serve to preventstalling at high angles of attack.
An optical filter is a device, which, by some particularmechanism, allows the transmission of some wavelengths, whilesuppressing others. The principal reason behind the use of filters inguidance systems is the necessity to suppress background IR radiation,such as reflected solar energy, or thermal radiation from the earth'ssurface and to enable the guidance to discriminate between variouspartsof the target's signature, as it wouldn't be very helpful to have a$20,000 missile guide into a ten metre long afterburner plume anddetonate without damaging the target.
Probably the most complex individual mechanical assembly in amissile guidance system is it's optical modulator or reticle. Itperforms two extremely important tasks, providing the system withdirectional target information and suppressing background IR radiation,In principle, a reticle is a IR transparent substrate with a particularpattern of opaque and transparent fields on it's surface.
By electronically filtering out these bursts, we can separatetarget information from clutter, the phase of the bursts yields theangular direction. The radial distance of the target can be found byexamining the amplitudes of the pulses, as the actual image of thetarget on the reticle is a circle rather than a point. The width of thesegments on the reticle is smaller than the circle's diameter, if thecircle is near the edge of the reticle a lot of light is passedthrough,if it is near the centre, very little is passed, causing the observedvariation in amplitude. Knowing the angular and radial components ofthetarget's direction, we can easily find the X and Y components withrespect to the missile's control axes, a computer can then find therequired control deflection for target interception. It may be apparentto many a reader that this system cannot provide target directioninformation if the reticle axis (missile axis) is pointing directly atthe target, actual operational systems employ complicated mechanicalsystems for the rotation and nutation of the optics and reticle toavoidthis.
The detector is a device which converts IR energy into someelectrical signal, which is then processed by the missile'selectronics.As a device, the detector comprises a piece of semiconductor material(the photosensitive element), with antireflective and/or filtercoatingsand a reflector, which increases sensitivity by reflecting any IR whichmay have passed through the detector back into it.
Heat seeking missile guidance is, after more than twenty fiveyears of use, anything but obsolete. New technology expands launchenvelopes and extends ranges with each new generation. of weapons. Somedevelopments in electronics (consider the recent fabrication of 30 x 30element arrays of HgCdTe on single mounting chips) may lead tocompletely different configurations in future weapons, the potential,for improvements is very large.
PICATINNY ARSENAL, N.J. - In the past several years, the proliferation of low-cost heat-seeking missiles has become a threat to United States military operations. As these weapons become more accessible to terrorist groups and third-world nations they become the weapon of choice for attacking Army helicopters.
For more than 20 years, the Pyrotechnics Research and Technology Division at Picatinny Arsenal has been at the forefront in developing technologies to protect military aircraft against heat-seeking missiles, said Picatinny engineer Andrew Zimmer.
I've lately started to realize that our most successful companies are led by entrepreneurs who have a unique talent -- they are heat seeking missiles. It doesn't matter where the missile is aimed pre-launch. Successful entrepreneurs are constantly collecting data -- and constantly looking for bigger and better targets, adjusting course if necessary. And when they find their target, they're able to lock-onto it -- regardless of how crowded the space becomes. When Nat and Zach first came to us with the idea for Invite Media, it was focused on algorithms for ad targeting. But once they got into the market the team saw a bigger opportunity -- the DSP space -- and they locked-onto that target with a successful outcome. We funded VideoEgg back in 2005 with the goal of creating tools to manage online video -- but Matt and team quickly adjusted course and have now become a leading media network for brand advertisers. When we first met Lance and Jia in 2006, they had a cool photo-hosting application called RockMySpace -- but they quickly found the opportunity was much larger than photo-hosting, and RockYou has since became a leading provider of social networking and gaming applications.
Markets really matter. Because the bigger the market, the more targets there are for the missile to hit. I've seen many companies fail to reach their potential because -- despite the skill of the founders -- they ultimately realize that there just aren't enough (or any) big targets for them to lock-onto. It's really hard to start a company -- and there are so many risks that all startups share, regardless of market size. Whether you're targeting a $10M addressable market or a $1B addressable market, you're still going to face Hiring Risk, Marketing Risk, Competitive Risk, Technology Risk, and Financing Risk. And while bigger markets might pose more challenges than smaller markets, the risks involved in targetting a $1B market are not 100x greater than those involved in $10M market. Choosing the right market is critical, because the market you choose determines the targets that are available for the heat-seeking missile to hit.
At the end of the day, I've really come to believe that you can't predict success based on where a missile is pointed pre-launch. Instead you have to assess the quality of the targeting system (the team) and the density/size of targets (the market). And hope that the missile you launch finds a true target -- rather than a decoy...
What CO2 does was confirmed by basic research that had absolutely nothing to do with climate change. (newsreel announcer) A continuance of the upper air program will provide scientific data concerning the physics of the upper atmosphere. (Richard Alley) World War II was over, but the Cold War had begun. The U.S. Air Force needed to understand the atmosphere for communications and to design heat-seeking missiles. 59ce067264